Category: 14187-32-7

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Macroheterocycles. 27. Amidomethylation of Benzo-crown Ethers

The synthesis of some novel benzo-crown ethers by alpha-amidomethylation is described.

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The Complexation of the Diquat Dication by Dibenzo-3n-crown-n Ethers

Spectrophotometric investigations of equimolar mixtures of diquat bis(hexafluorophosphate) (2) and a range of dibenzo-3n-crown-n ethers < n = 6-12; (10)-(16)> in acetonitrile reveal the existence of charge-transfer absorption bands at ca. lambdamax 400 nm.These absorptions are attributable to intermolecular ?-? charge transfer between the electron-rich catechol units of the dibenzo-crown ethers and the electron-deficient bipyridinium ring system of the diquat dication.The qualitative conclusion from these experiments, that the most stable 1:1 complex is formed between dibenzo-30-crown-10 (14) and diquat bis(hexafluorophosphate) (2), led to the isolation from dichloromethane methanol-n-heptane of red crystals of 2 suitable for X-ray crystallography.Although the crystal structure analysis revealed that there are two independent sets of 1:1 complexes (I and II) in the unit cell, the gross structural features of the two complexes are very similar.In addition to the paralell alignment of their three aromatic rings to accommodate the stabilising intermolecular ?-? charge-transfer interaction, there is probably some further host-guest stabilisation to be gained on account of favourable electrostatic interactions between the phenolic oxygen atoms in the host and the nitrogen atoms in the pyridinium rings of the guest.Moreover, there is some evidence for weak C-H…O hydrogen bonding involving principally H-6 and H-6′ on the bipyridinium ring system of the guest and certain -CH2OCH2- oxygen atoms in the host.As evidenced by 1H n.m.r. spectroscopy in CD3COCD3, these non-covalent bonding interactions are probably responsible for the formation of stable and ordered 1:1 complexes with similar gross structural features in solution, at least in the cases where dibenzo-30-crown-10 (14), dibenzo-33-crown-11 (15), and dibenzo-36-crown-12 (16) are the hosts.Further evidence for the 1:1 stoicheiometry of these solution complexes, as well as for the complex involving dibenzo-27-crown-9 (13), has come from equilibrium constant measurements for the association between the dibenzo-3n-crown-n (n = 9-12) hosts (13)-(16) and diquat bis(hexafluorophosphate) (2) in acetone.A quantitative treatment of the charge-transfer absorption bands at 400 nm, which affords Ka values of 410, 17500, 10800, and 2000 M-1 for n = 9, 10, 11, and 12, respectively, provides convincing quantitative evidence for (a) 1:1 stoicheiometry and (b) the relative stabilities of the 1:1 complexes in solution.In the case of dibenzo-24-crown-8 (11), a complex of 2:1 (guest-host) stoicheiometry is believed to be formed in acetone with a Ka value of 385000 M-2, as shown by a successfull quantitative treatment of the charge-transfer absorption data by an independent method.

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Complexation of macrocyclic compounds with metal ions: 2. Mg(II), Ca(II), Sr(II), Ba(II), Cu(II), and Ag(I) in 20 mass % propylene carbonate + ethylene carbonate

The conductance behavior of magnesium, calcium, strontium, barium, copper, and silver perchlorates and their complexes with seven crown ethers have been studied in 20 mass % propylene carbonate + ethylene carbonate. The conductance studies indicate 1:1 complex formation between the metal ion and crown ether. For the alkaline earth metal ions, the order of stability constants with all crown ethers is found to be Mg(II) > Ca(II) > Sr(II) > Ba(II). The limiting ionic conductivities of metal ions and the complexed metal ions are also reported. In addition, complexation studies of Cu(II) and Ag(I) were carried out by potentiometry and voltammetry to compare the results with those obtained by conductivity measurements, which were found to be in good agreement with each other.

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Further development of the structure-property concept on the basis of thermodynamic parameters of solvation

A thermodynamic study is made of the model systems consisting of a metal ion (Na, K), a crown ether (18-crown-6, dibenzo-18-crown-6), and an aqueous-organic solvent (water-methanol, water-2-propanol, water-acetonitrile). The contributions of reagent solvation to the strength and stability of mono complexes of crown ethers with alkali metal ions are found out. Attraction of the excess thermodynamic functions along with the complexation and solvation characteristics allows expansion of the capabilities of search and selection of biologically active compounds with desired properties on the basis of correlations between the bioligand structure and the process thermodynamics.

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Synthesis and crystal structure of two-dimensional network DB18-C-6 complex: [Na(DB18-C-6)]2[Pt(SCN)6]

A novel dibenzo-18-crown-6 (DB18-C-6) complex [Na(DB18- C-6)]2[Pt(SCN)6] (1) has been synthesized and characterized by elemental analysis, IR spectrum and X-ray diffraction analysis. The complex belongs to triclinic, space group P-1 with cell dimensions: a = 1.2500(3), b = 1.2825(3), c = 1.9342(4) nm, alpha = 106.82(3), beta = 102.51(3), gamma = 103.04(3), V = 2.7562 nm3, Z = 2, Dcalcd = 1.579 g/cm3, F(000) = 1316, R1 = 0.0364, wR2 = 0.0771. The complex shows a two-dimensional network structure of [Na(DB18-C-6)]+ complex cations and [Pt(SCN)6]2- complex anion bridged by Na-N interactions between adjacent [Na(DB18-C-6)]+ and [Pt(SCN)6]2- units.

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IR spectroscopic study of scandium extraction from sulfuric acid by solid-phase extractants based on tributyl phosphate, di-2-ethylhexylphosphoric acid, dibenzo-18-crown-6, and their mixtures

Solid-phase extractants (TVEKS) containing tributyl phosphate (TBP, I), di-2-ethylhexylphosphoric acid (D2EHPA, II), dibenzo-18-crown-6 (DB18C6, III), and their mixtures were prepared. The extraction of scandium by these extradants from a sulfuric acid solution with a concentration of 6 mol/l was studied. It was found by IR spectroscopy that in the extraction of scandium by TVEKS-III the Sc3+ ions were incorporated into macrocycle cavities to form a host-guest complex. The extraction of scandium by TVEKS-I occurred by a hydration-solvation mechanism: [TBP¡¤H3O]x + [Sc(SO4)y]¡¤zHSO4 -. In the synthesis of TVEKS-II. the conformation of D2EHPA was changed because of a decrease in the water content without formation of chemical bonds between the extradant and the polymer matrix. Based on IR spectroscopic data, a conclusion on the cation-exchange mechanism of scandium extraction by TVEKS-II was drawn. In TVEKS-(III + II) and TVEKS-(III + I), the crown ether interacted with an organophosphorus compound to result in an antagonistic effect in the extraction of the metal ion.

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Nuclear magnetic resonance study of the stoichiometry and stability of several Li+-crown ether complexes in various acetonitrile-nitrobenzene mixtures

Lithium-7 NMR spectrometry was used to study the complexation reaction between lithium ions and several 12-, 15- and 18-membered crown ethers in a number of binary acetonitrile-nitrobenzene mixtures. Formation constants of the resulting 1:1 complexes in different solvent mixtures were determined by computer fitting of the chemical shift-mole ratio data. There is an inverse relationship between the complex stability and the amount of acetonitrile in the mixed solvent. Among different sized crown ethers used, 15-crowns were found to form the most stable Li+ complexes in the series. The influence of substitution on the macrocyclic rings on the stability of the resulting complexes is discussed.

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Microwave-assisted synthesis of dibenzo-crown ethers

Microwave-assisted organic synthesis (MAOS) for dibenzo-substituted crown ethers is presented. Two routes were developed: (1) one-pot MAOS for symmetric dibenzo-crown ethers (DBC) and (2) a two-step MAOS via diphenol intermediates for both symmetric and asymmetric DBCs. MAOS were carried out in open or closed vessels, with or without temperature control at various microwave settings using different bases and reactants. Open vessel MAOS was limited by the volatility of reactants hence was less preferred than the closed vessel MAOS. DBC formation was highly affected by the cation size of the base, which acted as a template ion during DBCs ring closure. Closed vessel MAOS without temperature control was found most appropriate for DBC synthesis. Symmetric DBCs were conveniently obtained via one-pot MAOS whereas asymmetric DBCs were obtained from two-step MAOS via diphenol intermediates. The method was found expedient as it afforded satisfactory yields at considerably shorter reaction time than those in conventional methods.

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Preparation of a Polymer-supported Diol and Its Use in isolating Aldehydes and Ketones from Mixtures and as a Protecting Group for Aldehydes and Ketones

Reaction of cross-linked chloromethylated polystyrenes with 3-mercaptopropane-1,2-diol and sodium hydroxide under phase-transfer conditions gave polymers containing diol residues.A range of aldehydes and ketones were successfully bound to these polymers via acetal formation.The aldehydes and ketones were released by treating the products with aqueous dioxane in the presence of toluene-p-sulphonic acid.The polymer-supported diol could be used to isolate aldehydes or ketones from mixtures with other compounds and to separate a 3-oxosteroid from a 17- or a 20- oxosteroid.The supported diol was successfully used to protect the aldehyde group of undec-10-enal whilst the terminal vinyl group was transformed into -CH2CH2OCOPh.Attempts to monoprotect dicarbonyl compounds were unsuccessful.

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Solid (dibenzo-18-crown-6)KC60: Significant enhanced air-stability and appearance of a strong 13C NMR signal of C60- below 200 K with an unexpected negative chemical shift

Two novel properties, which arise primarily from intermolecular interactions between two aryl rings of the crown ether and neighbouring C60-, are found in solid (dibenzo-18-crown-6)KC60, viz. significantly enhanced air-stability and appearance of a strong 13C NMR signal of C60- below 200 K with an unexpectedly negative chemical shift.

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